Vehicle engines may include turbochargers, or superchargers configured to force more air mass into an engine's intake manifold and combustion chamber by compressing intake air with a turbine compressor. In some cases the compressor may be driven by a turbine disposed to capture energy from the flow of the engine exhaust gas. In transient and steady state operation of compressors, there is known Noise Vibration and Harshness (NVH) issues characterized by a whoosh noise, or simply whoosh. The whoosh condition, may cause undesirable or unacceptable levels of NVH, and may also lead to turbocharger/engine surge.
Attempts have been made to mitigate noise from turbocharger compressors. One attempt includes providing small channels to disturb the boundary layer of the incoming flow field to the turbocharger. Another attempt to mitigate turbine noise is disclosed in US Patent publication 2010/0098532 to Diemer et al. Diemer et al. attempts to reduce turbocharger stall noise by providing a groove that straddles the leading edge of the splitter blades of the compressor. The groove is located downstream from the leading edge of the main blades to provide a path for fluid around a rotating stall.
Other attempts to minimize compressor noise have provided various re-circulation passages wherein part of the flow is re-circulated from a downstream position to an upstream position via a passage separate from the main flow passage. One example of such an approach is disclosed in U.S. Pat. No. 7,942,625 to Sirakov et al. Sirakov provides a bleed passage downstream from the blade leading edge that enables a portion of the compressor fluid to re-circulate to an upstream location via an internal cavity and injection passage.
All these approaches fail to investigate the compressor flow path in the area of the main blade leading edge, and all fail to effectively address whoosh noise. In addition, none of these approaches target the broadband frequency range of whoosh noise with minimal effect on the flow field.
Embodiments in accordance with the present disclosure may provide a turbocharger including a casing having an inlet end and an outlet end. A flow passage may be provided within the casing that may have a substantially continuous inner surface and may be configured to pass inlet air from the inlet end to the outlet end. A compressor wheel may be located in the casing having at least one main blade and configured to rotate within the casing to compress the inlet air. A flow disrupting feature may be located on the casing and may be configured to disrupt the continuity of the inner surface. At least a portion of the flow disrupting feature may be located substantially in line with a leading edge of the at least one main blade and may be closed to upstream communication with the flow passage except via the flow passage.
Embodiments in accordance with the present disclosure may include a flow disrupting feature that may include a change in cross sectional area of the flow path that when located at the leading edge of the main blades of the compressor may decrease whoosh. Other embodiments may include a resonance chamber that may be tuned to mitigate certain whoosh frequencies.
Embodiments may include components of a flow disrupting feature that may be sized and proportioned in accordance with a particular mathematical formula which relates the components in a specified way to one or more particular frequencies of whoosh noise. In this way the broad band frequency range defined by whoosh can be targeted, and the whoosh issue reduced or mitigated.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.